Division for Foundations of Software

Division for Foundations of Software led by Professor Minoru Ito in graduate school of information science at Nara Institute of Science and Technology, JAPAN, focuses on the following most innovative and edge-cutting network technologies:

ITS aims to provide vehicle-to-vehicle (V2V) and vehicle-to-roadside communications so as to provide safety applications (like avoidance of car crash, notification of obstacles and safety message dissemination), traffic information (like, position of surrounding cars, car velocity, moving direction) and infotainment services (like games, video viewing, music sharing). For example, when a car got involved in an accident, it can directly communicate with other cars to inform them the accident so that others get alarmed and make corresponding decisions.

Cloud computing refers to the delivery of computing services (like software and information) from invisible providers hidden in cloud as illustrated in Fig.3. Instead of possessing one’s own hardware or software for computing task, one just needs to access these computing services from service providers through internet.

Regarding the above research topics, we focus on not only network applications that can be implemented directly in daily life, but also theoretical modeling that reveals the laws underlining network phenomenon that help us to better design network protocols.

Source delay, the time a packet experiences in its source node, serves as a fundamental quantity for delay performance analysis in networks. However, the source delay performance in highly dynamic mobile ad hoc networks (MANETs) is still largely unknown by now. This paper studies the source delay in MANETs based on a general packet dispatching scheme with dispatch limit f (PD-f for short), where a same packet will be dispatched out up to f times by its source node such that packet dispatching process can be flexibly controlled through a proper setting of f. We first apply the Quasi-Birth-and-Death (QBD) theory to develop a theoretical framework to capture the complex packet dispatching process in PD-f MANETs. With the help of the theoretical framework, we then derive the cumulative distribution function as well as mean and variance of the source delay in such networks. Finally, extensive simulation and theoretical results are provided to validate our source delay analysis and illustrate how source delay in MANETs is related to network parameters.

Understanding the fundamental end-to-end delay performance in mobile ad hoc networks (MANETs) is of great importance for supporting Quality of Service (QoS) guaranteed applications in such networks. While upper bounds and approximations for end-to-end delay in MANETs have been developed in literature, which usually introduce errors in delay analysis, the modeling of exact end-to-end delay in MANETs remains a technical challenge. This is partially due to the highly dynamical behaviors of MANETs, but also due to the lack of an efficient theoretical framework to capture such dynamics. This paper demonstrates the potential application of the powerful Quasi-Birth-and-Death (QBD) theory in tackling the challenging issue of exact end-to-end delay modeling in MANETs. We first apply the QBD theory to develop an efficient theoretical framework for capturing the complex dynamics in MANETs. We then show that with the help of this framework, closed form models can be derived for the analysis of exact end-to-end delay and also per node throughput capacity in MANETs. Simulation and numerical results are further provided to illustrate the efficiency of these QBD theory based models as well as our theoretical findings.